Explore the full potential of C++ by mastering the standard library.

Become a C++ Programmer

The C++ standard library is a collection of all the tools and utilities available in C++. It received its latest update in 2017, known as C++17. The update introduces many new features that further optimize our code. This module will help us fully grasp C++ and use it to its full potential.

C++ Standard Library

The reason for the constant access time of an unordered associative container is the hash function. The hash function maps the key to its value (its hash value). A hash function is good if it produces as few collisions as possible and equally distributes the keys onto the buckets. Because the execution of the hash function takes a constant amount of time, accessing the elements in the base case is also constant.

# The hash function

* is already defined for the built-in types like boolean, natural numbers, and floating point numbers.

* is available for `std::string` and `std::wstring`.

* generates, for a C string, `const char` a hash value of the pointer address.

* can be defined for *user-defined* data types.

For *user-defined* types, which are used as a key for an unordered associative container, we have to keep two requirements in mind: They need a hash function and an equality operator to be defined in order for them to be compared.

Here, we will understand why hash functions are essential in unordered associative pairs.

The Hash Function